Forces and motion

​How do you know?

Is this car moving?

How do you know?

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Is this car moving?

How fast? What direction?

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Are you moving?

Motion

An object is in motion if its position changes relative to another object

Reference Point and Relative motion

Reference point- a place or object to use for comparison to determine if something is in motion

Relative motion- motion can change based on the reference point

a push or a pull

forces can be used to speed up, slow down, and change direction

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Force

units of force

Named after Sir Isaac Newton

newton

Contact and non-contact forces

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​Types of Forces

When the objects actually touch one another

Examples include: push, pull, friction and normal force

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Contact forces

​The force that acts against gravity when a object is on a surface.

Always points perpendicular to the surface​

Normal Force

Acts against the motion of an object when making contact with a surface.
Always points the opposite direction of motion

Frictional force

A force that occurs without the objects touching

Examples: Gravity and magnetism

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Non-contact forces

Non-contact, attractional force that acts between any two objects that have mass

Objects with a larger mass, pull with a larger gravitational force.

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Gravitational force

Weight is an objects mass times the gravitational acceleration

Relative based on where you are (you weigh less on the moon and more "on" Jupiter

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What is weight?

Earth has a gravitational acceleration of 9.8 m/s²

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What is weight?

Net- final result after deductions

Net force- final "total" force after forces are added

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Net Force

If the net force on an object is zero (balanced) that object will not change its motion.

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Balanced and unbalanced forces

If the net force is not zero (unbalanced) the object will change its motion.

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Balanced and unbalanced forces

Force diagrams are used to show all of the forces acting on an object

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Force Diagrams

The length of the arrow represents the magnitude (value) of the force

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Force Diagrams

The length of the arrow represents the magnitude (value) of the force

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Force Diagrams

Get out your whiteboards now

Draw a force diagram to show the forces acting on the divers.

Draw a force diagram to show the forces acting on the box.

Draw a force diagram to show the forces acting on the moon.